A Chemical Approach to Raise Cell Voltage and Suppress Phase Transition in O3 Sodium Layered Oxide Electrodes

Abstract

Sodium ion batteries (NIBs) are one of the versatile technologies for low cost rechargeable batteries. O3-type layered sodium transition metal oxides (NaMO2, M = transition metal ions) are one of the most promising positive electrode materials, capacity-wise. However, the use of O3 phases is limited due to their low redox voltage and associated multiple phase transitions which are detrimental for long cycling. Herein, we proposed a simple strategy to successfully combat these issues. It consists in the introduction of a larger, non-transition metal ion Sn 4+ in NaMO2 to prepare a series of NaNi0.5Mn0.5-ySnyO2 (y=0-0.5) compositions with attractive electrochemical performances, namely for y=0.5, which shows a single phase transition from O3  P3 at the very end of the oxidation process. Na-ion NaNi0.5Sn0.5O2/C coin cells are shown to deliver an average cell voltage of 3.1 V with an excellent capacity retention as compared to an average step-wise voltage of ~2.8 V and limited capacity retention for the pure NaNi0.5Mn0.5O2 phase. This study potentially shows the way to manipulate the O3 NaMO2 for facilitating their practical use in NIBs.

Reaching the Energy Density Limit of Layered O3‐NaNi0.5Mn0.5O2 Electrodes via Dual Cu and Ti Substitution

“…[32] Could the beneficial role of Cu be the same within the layered NaNi 0.5 Mn 0.5 O 2 compound, in which the structure evolves through O3 → O′3 → P3 → O′3/P′3 (the prime symbol signifies the monoclinically distorted lattice compared to the hexagonal cell) → O-type as sodium is removed? [25] The major difference between the Cu-substituted and Cu-free samples nests in the extension of the P-type solid solution region for Cu-substituted NaNi 0. 5 Both materials were tested in an electrochemical cell equipped with a Be window, with Na as anode using C/30 rate and 4.5-2 V voltage window.…”

“…[12,19,20,22,25] It has been proved that the substitution of Mn 4+ (d3) in NaNi 0.5 Mn 0.5 O 2 by Ti 4+ (d0) increases the MO bond ionicity which in turn leads to higher charge localization on oxygen and thus a discrimination of Na sites. The studied O3 NaNi 0.5−y Cu y Mn 0.5−z Ti z O 2 (y = 0, 0.05, 0.1; z = 0.1, 0.2) phases with co-substitution of Cu 2+ and Ti 4+ were found to have an enhanced stability against structural phase changes at high potential, hence enabling to reversibly access ≈0.9 Na + (equivalent to ≈200 mAh g −1 ) in the extended voltage window (up to 4.5 V vs Na + /Na 0 ) with satisfactory cyclability.…”

Will Sodium Layered Oxides Ever Be Competitive for Sodium Ion Battery Applications?

“…1, respectively are in full agreement with previous findings. 21,[25][26][27][28][29] Whatever the O3 phase tested, a reversible capacity ranging from 100 to 150 mAh g −1 was observed when the cells were cycled between 2.2 V and 4 V. The discharge capacity is nearly equal to that of charge capacity with a small first cycle irreversibility (∼0.1 Na). On the other hand, the P2 phases behave quite differently.…”

Na 3 V 2 (PO 4 ) 3 @NC composite derived from polyaniline as cathode material for high‐rate and ultralong‐life sodium‐ion batteries

“…Similar to LIBs, the performance of SIBs largely depends on the cathode materials. At present, the study on cathode materials of SIBs is mainly concentrated on transition metal oxides, phosphates, pyrophosphate, and Prussian blues . However, the intrinsic properties of these materials, such as serious capacity decay and voltage platform receding because of structural variations during Na + ‐intercalation/removal process or occurring the side reaction, hinder their application in SIBs.…”

“…Similar to LIBs, the performance of SIBs largely depends on the cathode materials. At present, the study on cathode materials of SIBs is mainly concentrated on transition metal oxides, [11][12][13][14] phosphates, [15][16][17][18] pyrophosphate, [19][20][21][22][23] Abbreviations: CV, cyclic voltammetry; EIS, electrochemical impedance spectroscopy Please proceed accordingly; FT-IR, fourier transform infrared; LIBs, lithium-ion batteries; NVP@NC, N-doped carbon-composited Na 3 V 2 (PO 4 ) 3 ; NVP/C, carbon-composited Na 3 V 2 (PO 4 ) 3 ; NC, N-doped carbon layer; NVP, Na 3 V 2 (PO 4 ) 3 ; PAN, polyaniline; PVDF, polyvinylidene fluoride; SEM, scanning electron microscopy; SIBs, sodium ion batteries; TEM, transmission electron microscopy; TG, thermogravimetric; XPS, X-ray photoelectron spectrometer; XRD, powder X-ray diffraction. and Prussian blues.…”